I picture a navigation bar that includes new navigation elements to jump to the next or previous answer in the current question. See mockup below:
Since devinb's comment here makes a good point, I propose making the top bar optionally floating on top, just like the notification bar. In fact, I'd like this to replace notifications by an additional Symbol, e.g.
!! which could, just like the brand new StackExchange logo, popup into the unread notifications.
Once again, the floating on top should be optional